1. Technical Field
The present invention relates to an automotive rotary electrical apparatus mounted on a vehicle such as an automobile, and in particular to an automotive rotary electrical apparatus provided with a rotary electric machine having an armature coil and a field coil and coupled to an engine mounted on the vehicle, and a control device having a battery terminal connected to a positive terminal of an in vehicle battery, a common potential terminal connected to a common potential point, and positive and negative field terminals connected to the field coil.
2. Related Art
The control device in the automotive rotary electrical apparatus of this kind includes a field drive circuit forming a feeder circuit for the field coil, and a field control circuit for controlling the field drive circuit. In the case in which the rotary electric machine is configured as a generator, the field drive circuit generally includes only one switching control element and only one diode element. The switching control element is connected between the battery terminal and the positive field terminal, and the negative field terminal is connected to the common potential point. The field coil is supplied with electricity from the in-vehicle battery via the switching control element. The field current flowing through the field coil is controlled based on an on/off operation of the switching control element, thus an output voltage of the armature coil of the generator is controlled. The diode element is connected between the positive field terminal and the negative field terminal in parallel to the field coil so that the cathode thereof is connected to the positive field terminal. The diode element passes a circulating field current in accordance with a transient voltage caused in the field coil to protect the switching control element when the switching control element is turned off.
However, in the field drive circuit described above including one switching control element and one diode element, when a short-to-power malfunction, namely a malfunction that the positive field terminal has direct contact with the battery terminal, is caused in the field coil, or a short-circuit malfunction is caused in the switching control element, blocking of the field current flowing through the field coil is not achieved.
JP-2006-288082A (Document 1) discloses a control circuit for an automotive generator having a field drive circuit formed of an H bridge using four switching control elements. The H-bridge has the switching control elements respectively connected to four side arms thereof, and the field coil is connected between a midpoint of one pair of switching control elements and a midpoint of the other pair of switching control elements. By using the H-bridge, when a malfunction is caused in either one of the four switching control elements, the malfunction can be avoided.
However, in the control device of the automotive generator described in the Document 1, since the four switching control elements are used, the control therefore becomes complicated.